Rotating agitator for a cylindrical receptacle of great length

ABSTRACT

A rotary agitator for use in a long cylindrical container, which may for example, be a chemical processing or reaction chamber. The agitator has two bearing members which cooperate with bearings in the container to support the agitator in the container. A plurality of helical blades are connected directly to each of the bearing members. A number of lattice rods are connected between the blades and the bearing members, and between the blades themselves. The bearings, blades and rods may be hollow and may define flow paths for cooling fluid.

United States Patent 1191 1111 3,820,761 Rigal 1451 June 2s, 1974 [54]ROTATING AGITATOR FOR A 3,043,571 7/1962 swanhom 259/105 x CYLINDRICALRECEPTACLE OF GREATl LENGTH Inventor: Jean Rigal, Saint-Etienne, FranceAssignee: CreusotLoire, Paris, France Filed: Mar. 23, 1972 Appl.115.1231269 Foreign Application Priority Data Mar. 26, 1971 France71.10816 U.S. Cl. 259/109, 416/227 Int. Cl ,B01f 7/02 Field of Search259/9, l0, 25, 26, 45,

` References Cited UNITED STATES PATENTS 10/1960 Moultrie 259/105Primary Examiner-Harvey C. Hornsby Assistant Examiner-Philip R. Coe

ABSTRACT 3 Claims, 2 Drawing Figures ROTATING AGITATOR FOR A CYLINDRICALRECEPTACLE OF GREAT LENGTH This invention relates to a rotary agitatorfor a long cylindrical container. Thetagitator is particularly useful,for example, for a horizontal-axis chemical reactor for the productionof certain basic polymers.

For efficient operation of such a reactor, and, in particular, to avoidaccumulation of material on the reactor walls, the clearance between theagitator and the walls must b`e as small as possible. The minimisationof the radial clearance 'between the agitator blades and the innersurface of the container wall is limited both by the ordinary initialproduction tolerances and by deformation that the agitator undergoes inoperation due 4to forces applied to it during agitation of the materialin the container. The simplest and bestknown solution is therefore tomake the agitator in the form of a robust and rigid central shaft withperipheral blades connected thereto by radiating arms. ln conventionalconstructions, the blades `are usually helical and are hollow, thecentral shaft of the agitator and the arms providing the connectionbetween the shaft and the blades being also hollow; this arrangementallows fluid to flow inside the agitator elements` in order either toheat or cool the mixture being processed in the container.

Development in the plastics production industry has resulted inprocessing containers of ever-increasing volume being required. It hasalso been found lthat in order to obtain suitable homogeneity of theproducts the diameter of the container must be limited, the increased`volume required therefore being obtained by increasing the length ofthe containers. Consequently,

the central shaft of the agitator becomes increasingly longer and itsdiameter has to be increased to give it sufficient rigidity to ensureminimum clearances between the agitator blades and the container wall.This shaft diameter increase results in a reduction of the proportion ofthe volume of the container available for containing processing materialand therefore a considerable increase in weight of the processingapparatus and hence a much higher cost price. The length of such a shaftis also limited because of the dimensional limitations of machinescapable of machining the trunnion bearings. i

The object of the invention is to provide a rotary agitator having amuch higher structural rigidity than known agitators made from acomparable amount of metal, so that longer chemical-reaction containerscan be produced.

According to the invention there is provided a rotary agitator for acontainer comprising a plurality of bearing-members separatedlongitudinally of the agitator for cooperation with the bearings in thecontainer, a plurality of helical blades each coupled directly and by atleast one lattice rod to each of the bearing members, and coupled toeach other by a plurality of said lattice rods.

In a preferred embodiment of the invention applied to cases in which theblades are hollow and carry a flow of fluid through the agitatortrunnions, the lattice rods are hollow and the internal chambers ofthese rods communicate with the internal chambers of the blades.

The invention will now be described in greater detail with reference toa specific embodiment given by way of example and shown in the drawings,in which:`

FIG. 1 is a side view of an agitator according to the invention, showingthe ends of the agitator and connection to the trunnions; and

FIG. v2 is an end view of the agitator.

The agitator is intended to be used in a generally cylindrical containerl, the inside profile of which is shown in chain-dotted lines in thedrawings. Both ends la of the container are of a conventional domedshape. At each end, the agitator rests via a trunnion 2 on a bearing 2aconnected to the agitator body; these bearings are shown in the drawingsand may be of any conventiona] type, for example,ysealed bearings if thecontainer is to be operated under internal pressure.

The agitator operating members consist essentially of three helicalblades 3, 4 and 5. In the specific case shown in the drawing, theseblades consist of anglemembers so constructed that their angle is alwaysdirectedtowards the axis of the container. Towards its inner end, thetrunnion 2 bears three radial arms 7, 8 and 9, each provided at oneendwith a support 10, 11 and 12 having an angled notch of the sameprofile as the angle-section forming each of the blades. Each support,10, 11 or 12, is also connected to the trunnion 2 by a rod 13 acting asa strut.

Each blade, for example blade 3, is secured at l5 to the trunnion 2, andis then fitted into the `groove of the support 10 with a curvature verysimilar to the internal curvature of the tank end, and then continuesYin the form of a purely helical part over an outside coil diameterslightly less, to allow the necessary clearance, than the insidediameter of the container. In a series of transverse planesperpendicular to the axis of the apparatus and, for example, axiallyequidistant, each helical blade 3, 4 or 5 is connected to a support 1S,16 and 17 respectively, in which they are each fitted. Eachoi` thesupports of the same transverse plane is connected to the other two by afirst set of rods 18 which form an equilateral triangle. Each support15, 16 or 17 is also connected by a rod to a support of the precedingtrans verse planeassociated with another blade, and to a sup port of thenext transverse plane associated with the third blade. Thus the support17' associated with the blade 5 is connected to the support 1lassociated with the blade 4 and to a support 20 associated with theblade 3. Similarly, the support 16 associated with the blade 4 isconnected to the support 10 associated with the blade 3 and to a support22 associated with the blade S.

The agitator thus constructed according to the inven tion forms athree-dimensional lattice structure which allows the agitation blades tobe used as the main frame members. The blades forming the frame membersare remote from the central axis of the apparatus so that improvedassembly rigidity is obtained for a smaller amount of metal used.

The elimination of the central shaft improves access to the interior ofthe container for maintenance and cleaning operations and for the normalsizes of such containers used as chemical processing containers, al lowsman access to the interior of the apparatus.

This method of construction also means that it is possible to departfrom the limited size of existing machines, because it is no longernecessary to mount the agitator on a lathe to machine the trunnions.This removes one of the limitations in the possible sizes of thecontainers and their agitators.

The blades of the agitator may be hollow as at 4a to allow fluid to flowthrough them for cooling or heating of the product being processed. Thisis already known in the case of conventional central-shaft agitatorshaving radiating arms supporting the blades. In such cases the shaft 2is hollow as at 2b and the same applies to the arms connecting it to theblades as at 9a. The agitator according to the invention also allowsthis fluid flow by the provision of tubular-section blades; since thesupports to which the connecting arms are joined are also hollow as at12a, as are the rods themselves, there is a complete interconnection ofall the internal chambers of the agitator elements.

In the arrangement described above, each support forming a connectingrod junction comprises an even number of outlets, thus allowing an equaldistribution of the fluid in the various blades.

I claim:

l. A rotary agitator comprising a cylindrical container having a longhorizontal axis, ends for said cylindrical container, a bearing in eachof said ends, trunnions rotatably mounted in each of said bearings,three 1 helicoidal spaced blades in said container closely spaced to theinternal wall of said container and each of said blades being connectedto each of said trunnions and rotating about an axis coincident with thelong axis of said container, means for connecting each of said blades atregular intervals to the other two of said blades including a bardisposed in a plane perpendicular to the long axis of said container anda bar oblique with respect to said plane, said two bars, relative toeach of the other bars of said two other blades, being disposed onopposite sides of said perpendicular plane.

duit openings.

l l a k

1. A rotary agitator comprising a cylindrical container having a longhorizontal axis, ends for said cylindrical container, a bearing in eachof said ends, trunnions rotatably mounted in each of said bearings,three helicoidal spaced blades in said container closely spaced to theinternal wall of said container and each of said blades being connectedto each of said trunnions and rotating about an axis coincident with thelong axis of said container, means for connecting each of said blades atregular intervals to the other two of said blades including a bardisposed in a plane perpendicular to the long axis of said container anda bar oblique with respect to said plane, said two bars, relative toeach of the other bars of said two other blades, being disposed onopposite sides of said perpendicular plane.
 2. A rotary agitator asclaimed in claim 1, wherein the bearings, helical blades and said barsare all hollow and define a plurality of flow paths for the flow offluid through the agitator.
 3. A rotary agitator as claimed in claim 2wherein said bars are coupled together and to the helical blades at aplurality of connecting junctions, each said connecting junction havingthe same number of fluid conduit openings.